The Byron Smartwares B305 Wireless Plug-In Chime has a 50 metre operating distance. It provides a choice of two melodies and has volume control. It features self-learning codes and will keep the code even when the batteries run out and are replaced. This Plug-in chime can have up to 2 bell pushes controlling the chime. It has a 80-85dB rating, depending on the sound. Compatible with all Byron B ranges. The plug-in chime is mains powered. The push requires 1 x 23A battery (included).